Electron beam deflecting system



May 6, 1958 E. GUNDERT ET AL 2,833,947

ELECTBON BEAMl DEFLECTING SYSTEM i Filed Oct. 20. 1953 5 Sheets-Sheet l 1 E Ilfllllllll May 6, 1958 E. GUNDERT Er Ax. 2,833,947

ELEcTRoN BEAM DEFLECTING SYSTEM .Im/entors- BBRHARD 60A/DEW WERNER KLUGE mamey May 6, 1958 E. GUNDERT ET AL 2,833,947

ELECTRON BEAM DEF'LECTING SYSTEM l Filed 00T.. 20, 1953 y 5 Sheets-Sheet 3 [n1/enfans ZGERHHRD (yuh/.D597 wERwR KLUvE B mnu; S. Smm ATTORNEY May 6, 1958 E. GUNDERT Er AL 2,833,947

ELEcTRoN BEAM DEFLECTING SYSTEM Filed Oct. 20. 1953 5 Sheets-Sheet 4 May 6, 1958 E. GUNDERT ET AL` 2,833,947

ELECTRON BEAM DEFLECTING SYSTEM Filed Oct. 20, 1953 5 Sheets-Sheet 5 WERNER KLu- (um S; 561.02m/ rbmef Unite tates Patent ELnCTRoN BEAM DnFLEcrnsG SYSTEM Eberhard Gnndert and Werner Kluge, Ulm (Danube), Germany, assiguors to Telefunken Gesellschaft fur Drahtlose Telegraplne rn. b. H., Hannover, Germany Application October 20, 1953, Serial No. 387,122

Claims priority, application Germany October 28, 1952 s claims. (cl. 31a-7s) The present invention relates mainly to electron beam sysems, and more particularly to electrostatic deection systems for cathode ray tubes.

It is generally known that cathode ray tubes employing electrostatic deection systems may be operated with balanced as well as unbalanced decction circuits. It is furthermore known that pattern distortions, of the type known as trapezoidal and pin-cushion distortion, appear in cathode ray tubes employing electrostatic deflection systems.

If a cathode ray tube, employing an electrostatic deection system, is operated with balanced detiection circuits no trapezoidal distortion will be noted. The circuit arrangement is however simplied if unbalanceddeection circuits are employed and therefore such arrangements are preferred. ln unbalanced deection circuits one ot the deflection plates adjacent the screen of the cathode ray tube is connected to the anode thereof, while the other deection plate has the detlecting or control voltage connected thereto.

Various techniques for overcoming and eliminating trapezoidal distortion resulting from the use of unbalanced deecting circuits are known. One known technique is to construct the pair of deflection plates adjacent the screen of the cathode ray tube asymmetrically, by for instance, making the deection plate, to which the deection voltage is connected, U-shaped. In this manner trapezoidal distortion is avoided when using unbalanced deflection circuits for cathode ray tubes using electrostatic deection systems.

Although trapezoidal distortion is eliminated, as noted, by the U-shaped construction of one of the deflection plates adjacent the screen when using unbalanced deflection circuits, it has been noted that trapezoidal distortion will again arise when such construction is used with balanced deilection circuits.

Pin-cushion distortion results because the electron beam in its undeected state passes between a pair of dellecting plates, located near the image screen, in a shorter time than when said electron beam is deected by' means of the deflection plates located near the cathode end ofthe cathode ray tube. As a result the deflection sensitivity of the deection plates adjacent the screen is greater for the detlected than for the undeflected beam.

Various techniques for decreasing or neutralizing pin cushion distortion are known. These techniques have the disadvantage, however, that while serving to reduce pin cushion distortion, they tend to increase trapezoidal distortion. The known techniques for decreasing or--neu-v ICC The invention is based on the realization that afore- I mentioned distortions may be reduced if the deflecting plates adjacent the image screen end of the -tube are so constructed that the electron beam in every position of its deection, produced by the deecvting plates near the cathode end of the tube, is exposed while passing through the l deecting plates adjacent the screen to a uniformelectrostatic iield. At the same time, the vimage screen should be so constructed that the electron beamupon leaving the deflecting plates located at the image screen end of the tube covers the same distance to the screen.

The beneficial results of the invention are realized by providing the dellecting plates located adjacent the image screen end of the tube with arcuate edges extending substantially transversely to the principal axis of the tube in the form of arcs whose centers of curvature are located in a center line passing through the principal axis perpendicular thereto and to the plane of deflection of the detlecting plates` adjacent the cathode end of the cathode ray tube. Ideally the center line should also pass through the mid deflection point of the deecting plates adjacent the cathode end of the tube. In order to completely eliminate trapezoidal and pin-cushion distortion the image screen should likewise have its center of curvature located substantially at the mid deflection point.

From the above discussion it will be apparent that the primary object of the present invention is to provide a cathode ray tube employing electrostatic deflection sys` tems and which may be used with balanced as well as unbalanced electrostatic deflection.

Itis another object of this invention to substantially reduce image distortion prevalent in present day cathode ray tubes employing electrostatic deflection systems..

It is yet another object of the present invention to provide Aa cathode ray tube whosek image screen rnayfbe'l spherical, slightly sphericaly or even non-spherical without danger of introducing excessive trapezoidal or pin"- cushion distortion.

An embodiment of the present invention involvesan i electron beam deflecting system for cathode ray tubes embodying means for emitting anelectron beam along a principal axisA comprising first electron beam deecting means fordeilecting an emitted electron beam in a predetermined plaue of deection; second electron beam deflectingmeans including a pair'of defiecting plates located in direction of they principal axis after and spaced from the first electron beam deflecting means on opposite sides of the principal axis, 'the 'deecting plates having arcuate edges extending substantially transversely to the principal axis in the form of arcs whosecenters of curvature are located in a centerline passing through the principal axis perpendicular thereto and to thepredetermined plane of deflection. f

Another embodiment `of thev present invention Uitl-'v'4 2gsm-947 volvesan electron beam deecting system Afor cathode ray tubes embodying means for emitting an electron beam along a principal axis comprising, rst electron beam deecting means for deflecting an emitted electron beam in a predetermined plane of deflection, and second electron beam deecting means including a pair of `deilecting plates located in direction of the principal axis after and spaced from the lirst electron beam deflecting means on opposite sides of the principal axis, said deecting plates having' arcuate entrance edges extending substantially transversely to the principal axis in the form of arcs whose centers of .curvature are located in a rst line passing through a first point of the principal axis perpendicular thereto'and to the predetermined plane of deection and having exit edges extending substantially transversely to saidA principalaxis in the form of arcs Whose centers of curvature are located in a second center line passing through said principal' axis parallel to the irst ce'nft'efr line and at a second point of said principal axis located between the r'st point of `said principal axis and they deiiectingj plates.

Yet ano'ther'embodime'nt of the' present invention involves an electron beam'deecting system for cathode ray tubes comprising means for emitting an electron beam alongl a principalA axis, iirst electronV beam deecting means for deectin'g tleY emitted electron beam, the deecting means having` a midv deflection point located in the principal' axis fromwhich the electron beam is detle'ctedin a" predetermined plane of deflection, second electron beam deecting' means including apair of deliecting plates located in direction of the principal axis vafter and spaced from the lir'st electron beam deecting means on opposite sides of the principal axis, the deilectingr plates hayirig'- enti-ance and exit edges extending sub s stantially transversely to theA principal axis in the form ofarcs Whose centers" of curvature are located in a center line passing through the mid deliection point perpendiculafr tothe' principal axis and to the predeterminedplane of deection, an image screen havingA a spherical face whose center of curvature is located substantially in the mid detlectiori point.

The novely features which are considered as characv teristic forl the invention are set forth in particular in arrsws;

Fig. 3 is arvertical sectionvof Eig. 2 taken along` lines 3-3 in thedirection ofthe arrows;

Fig. 4 is a vertical section similar to Fig. 2 and serves toillustrate a modication of the present invention; and

Fig. 5 is a vertical section similar to Figs. 2 and 4 and illustrates yet another modification of the present invention. j

Referring to Fig. l, avacuum envelope-1 isillustrated, in which there is arranged an electron gun- 3. and an electrostatic deflectionl system. The electrodes ot the electron gun 3, as well as thedeecting plates adjacent the cathode and screen ends of the cathode ray tube, respectively, are secured by means of clamps 4' to the insulating rods 4. The electron gun 3 and deliecting plates 6 and 7 are united to form a single assembly which is insertedinto, the neck portion Z- of the vacuum envelope; and` supported therein; by means of bracing springs 5. The deecting plates 6 and 7 are arrangedin 90`re1ationvtho each other so that onepairof plates will detiect the electron beam horizontally, while the other will lie in a 2nd center line 17 which is parallel tothe.

pair of platesvserve to deect the beam in vertical direction. The shape of the pair of deflecting plates 7 is illustrated in Fig. 1. Due to the particular shape of these plates trapezoidal and pin-cushion distortion is substantially eliminated.

Figs. 2 and 3 illustrate the pair of deecting plates 7 as consisting of three individual sections 8, 9 and 10 which diverge in the direction of the screen 14. By diverging the deiiecting plates adjacent the screen end of the tube the deflection sensitivity can be increased since the electron beam may be kept close to the plates without actually hitting the plates. Y

In accordance with the invention the deflecting plates 7 have arcuate exit and entrance edges 14, 14a respectively, extendingsubstantially transversely to the principal axis 13 in the form. of arcswhose centers of curvature are located in a center line passing through the principal axis lfperpfendicular thereto and to the plane of-dellection of the deecting plates 6. The center line in this case should'spreferably pass through the mid deection point 11 of the deecting plates 6. Asmay be noted in Fig. 2 the beam entrance edge 14 is generated by a radius R1 whereas the beam exit edge 14a is generated by.|` arradius R2. The image screen in this case has a spherical face whose center of curvature is located' sub'- stantially in the mid deiiectionpoint 11 and whose radiusisdenotedbyls. Sections 9 and 10 are parts of cones havingiavcommon axis located in the center line passing through the principal` axis 13L The deecting plates 7 can'also be made as aV single continuous section instead' of' the three .sections illustrated in Figs. 2` and 3.

lf: thatl image screen is` constructed as illustrated in Fig. 2, neither trapezoidal nor pin-cushion distortioncani'. re'sult. A'sar rnlebccause of the elort to obtain betterv imag'efreproduction, a plane image screen or an tralized; 'Ehe-neutralization of pin-cushiondistor-tion is elected by displacing the center of curvature of exit edge 15iandr also-oil exib edges ofthev parts'8 andf9', iff the deiiecting. plates: 7 consist ofthree individual sectionsl as illustrated?inlig; 2 toward. the imagescreen 16. In this embodimentlthel center: of curvature of the arcuate entrance edge: 14iremainsfin" the same center line passing throughuthefmid-deection point 1-1" as inA thev case ofthe embodiment illustrated in' Figs. 2 and 3'. This center linerwillihencefortht be referred' to as the first center line. Theicenteiof'curvature of the arcuate-beam exit' edge 15- iifstcenter line' and perpendicular to the principal' axis.

Since' the image screen` 161m' this case is but slightly curv'editsfcenter of curvature will' belocated in a1 pointv on-A theiprincipalfaxi's farther from the image screenrk thanV the: ni-deflection point 11. By displacing the center of curvature of the arcuate exit edge-1S from its position illustratedlin Fig. 2 to the position illustrated inv Fig. 4,

theelectronbeamin its undeected condition w-illfbe connedbetwee'n the' dellecting plates 7 for a greater distance than in'` its deflectedE condition, which deflection is produced? by al pair 'of dellectingplates' 6;

R1', R2, and Rfa illustrate respectively the radii of the arcuate-beam entrancev edge 14, the arcuatev beam entrance edge 15, and` the` spherical face of the image screen 16.-, Inftliis embodiment the. detlecting plate 17 is illustrat'ed' as'beingr constituted of a single continuous section.

In order to: neutralize: trapezoidal distortion which re- Slll because, of: at slight deviation from the rotational' symmetry-oli the.. plates' 7.,- for instance because of' the omissionof a'rscreen. normally located between; thel image.-

if the beam;.entrance.edge .illustratedin Fig, Svasf well as the beam exit edge have their centers of curvature respectively displacedtoward the image screen, that this trapezoidal. distortion` may` beV substantially reduced. As clearly indicated in Fig. .5 the arcuatefbeam entrance edge has; a radiussRLandacenter of curvature which is 1ocated in affirst centerv line 19 andan arcuateexit edge whichhasa radius Rzanda center of curvature located inral secondrcenter line 20, the first and fsecond linesbeing parallel to each other and perpendicular to the principal axis 13. 'Ihe image screen is illustrated as having a radius R3. By means of this modification it is possible to eliminate trapezoidal and pin-cushion distortion for cathode ray tubes which are not completely rotationally symmetrically constructed.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of electron beam detlecting systems diiering from the types described above.

While the invention has been illustrated and described as embodied in cathode ray tubes, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specic aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. In an electron beam deecting system for cathode ray tubes embodying means for emitting an electron beam along a principal axis, in combination, first electron beam detiecting means for deecting an emitted electron beam in a predetermined plane of deflection; and second electronbeam deecting means including a pair of deflecting plates located in direction of the principal axis after and spaced from said first electron beam dellecting means on opposite sides of said principal axis, said deecting plates having entrance edges extending substantially transversely to said principal axis in the form of arcs Whose centers of curvature are located in a first center line passing through a first point of said principal axis perpendicular thereto and to said predetermined plane of detiection and having arcuate exit edges extending substantially transversely to said principal axis in the form of arcs whose centers of curvature are located in a second center line passing through said principal axis parallelto said first center line and at a second point of said principal axis located between said iirst point of said principal axis and said deecting plates.

2. In an electron beam deecting system for cathode ray tubes embodying means for emitting an electron beam along a principal axis, in combination, first electron beam deecting means for deecting an emitted electron beam, said deecting means having a mid-deliection point located in the principal axis from which said electron beam is deected in a predetermined plane of deiiection; and second electron beam deecting means including a pair of deecting plates located in direction of the principal axis after and spaced from said lirst electron beam deecting means on opposite sides of said principal axis, said deecting plates having arcuate entrance edges extending substantially transversely to said principal axis in the form of arc whose centers of curvature are located in a first center line passing through said mid-deflection point perpendicular to said principal axis and to said predetermined plane of deflection and having arcuate exit edges extending substantially transversely to said princiof deflecting plates located in direction of the principal axis after and spaced from said rst electron beam deilecting means on opposite sides of said principal axis, said deecting plates having entrance edges extending substantially transversely to said principal axis in the form of arcs whose centers of curvature are located in a rst center line passing through a first point of said principal axis perpendicular thereto and to said predetermined plane of deflection and having arcuate exit edges extending substantially transversely to said principal axis in the form of arcs whose centers of curvature are located in a second center line passing through said principal axis parallel to said first center line and at a second point of said principal axis located between said iirst point of said principal axis and said detlecting plates; and an image screen having a spherical face whose center of curvature is located on said principal axis farther I from said image screen than said tirst point of said principal axis.

4. In a cathode ray tube in combination, means for emitting an electron beam along a principal axis; first electron beam deflecting means for deflecting said emitted electron beam, said deilecting means having a mid-deflection point located in said principal axis from which said electron beam is deected in a predetermined plane of deflection; second electron beam deflecting means including a pair of deecting plates located in direction of the principal axis after and spaced from said rst electron beam deflecting means on opposite sides of said principal axis, said deflecting plates having arcuate en- .trance edges extending substantially transversely to said principal axis in the form of arcs Whose centers of curvature are located in a iirst center line passing through said mid-deection point perpendicular to said principal axis and to said predetermined plane of deflection and having arcuate exit edges extending substantially transversely to said principal axis in the form of arcs whose center of curvature are located in a second center line passing through said principal axis parallel to said first center line and at a point of said principal axis located between said mid-deflection point on said principal axis and said deecting plates; and an image screen having a spherical face whose center of curvature is located on said principal axis farther from said image screen than said mid-deection point of said lirst electron beam deflecting means.

5. In a cathode ray tube in combination means for emitting an electron beam along a principal axis; tirst electron beam deecting means for deflecting said emitted electron beam, said deflecting means having a mid-deiiection point located in said principal axis from which said electron beam is deected in a predetermined plane of deection; second electron beam deliecting means including a pair of deecting plates located in direction of the principal axis after and spaced from said rst electron beam deecting means on opposite sides of said principal axis, said deflecting plates having entrance edges extending substantially transversely to said principal axis in the form of arcs whose centers of curvature are located in a first center line located perpendicular to said principal axis and to said predetermined plane of deflection and passing through said principal axis at a first point thereof located between said mid-deflection point and said deecting plates, said deilecting plates having also exit edges extending substantially transversely 7 to said principai axis in the form of arcs whose centers of curvature are located in a second center line passing through said principal axis parallel to said irst center line and at a second point of said principal axis located between said iirst point of said principal axis and said deecting plates; and an image screen having a curved face the radius of curvature of which at any point thereof is greater than the distance between said mid-deflection point and said image screen.

UNITED STATES PATENTS Ressier Apr. 19, 1938 Schlesinger Aug. 9, 1938 Ruska Mar. 28, 1939 Du Mont June 20, 1939 George ;Nov. 26, 1940 Shelton Oct. 3, 1950 

